Audio input unit, audio input method and audio input and output unit

ABSTRACT

A videoconferencing system uses an audio input unit including: two directional microphones disposed in directions with directivity being opposite to each other, the microphones forming a pair and a plurality of the pairs being located with directivity shifted from each other, cancellation elements for canceling sound components of the same phase from sounds inputted to the microphones of the pair, extraction elements for extracting sound components of voice band from sounds inputted to the microphones of the pair, a calculation element for calculating a difference between levels of the sound components of voice band extracted by the extraction elements to decide the microphone which has the larger level in the pair having the largest level difference, and selection elements for selecting sounds as input sound, in which the sound components with the same phase are canceled by the cancellation elements from sound inputted to the microphone decided by the calculation element.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an audio input unit, an audio inputmethod and an audio input and output unit for use in a remote conferencesystem such as a videoconferencing system.

2. Description of the Related Art

Many departments or companies have so far introduced systems by whichparticipants at a plurality of remote locations can attend a meeting bysending and receiving audio signals transmitted through a high-speedline.

FIG. 1 of the accompanying drawings is a block diagram showing anoutline of a videoconferencing system which is a kind of such remoteconference systems. As shown in FIG. 1, a meeting room Ra includes amicrophone 101 a, a speaker 102 a, an echo canceller 103 a, a videocamera 104 a, a projector 105 a, a codec 106 a and a DSU (DigitalService Unit) 107 a.

As shown in FIG. 1, a meeting room Rb at a location remote from themeeting room Ra includes a microphone 101 b, a speaker 102 b, an echocanceller 103 b, a video camera 104 b, a projector 105 b, a codec 106 band a DSU 107 b as well. The DSU 107 a and the DSU 107 b are connectedto each other through a dedicated line 108 or an ISDN 109.

The echo cancellers 103 a, 103 b are adapted to suppress echo caused bya phenomenon in which sounds inputted to microphones of one side areagain outputted from the speakers of its own side after the sounds havebeen outputted from the speakers of another side and inputted to thespeaker of another side, and to suppress howl caused by such echo. Theecho cancellers 103 a, 103 b are constituted by installing, for example,digital filter software in a DSP (Digital Signal Processor).

A voice of a participant in the meeting room Ra is inputted to themicrophone 101 a and outputted from the speaker 102 b in the meetingroom Rb through the echo canceller 103 a, the codec 106 a, the DSU 107a, the dedicated line 108 or the ISDN 109, the DSU 107 b, the codec 106b and the echo canceller 103 b, sequentially. A voice of a participantin the meeting room Rb is also inputted to the microphone 101 b andoutputted from the speaker 102 a in the meeting room Ra.

A known system to hold a meeting by sending and receiving voices among aplurality of remote locations through a high-speed line like thisvideoconferencing system (referred to as a “remote location meetingsystem” in this specification) has so far employed the following system(1), (2) or (3) as a system for inputting voices of participants throughmicrophones when a plurality of participants are sitting at onelocation.

(1): One non-directional microphone is set in a meeting room and soundinputted to this non-directional microphone is directly supplied to anecho canceller.

(2): A plurality of directional microphones as a whole are set at thecenter of a table at which participants are sitting in such a mannerthat voices from all participants may be inputted to the microphones(voices from every part of seats can be inputted to individualdirectional microphone). Voices inputted to the respective directionalmicrophones are synthesized and supplied to an echo canceller.

(3): A plurality of directional microphones as a whole are set at thecenter of a table at which participants are sitting in such a mannerthat voices from all participants may be inputted to the microphones(voices from every part of seats can be inputted to individualdirectional microphone). Then, a microphone to which sound of levelexceeding a predetermined reference level (ordinary noise level withinthe meeting room) is inputted is selected from these directionalmicrophones and only the sound inputted to the microphone is supplied tothe echo canceller.

So far this remote location meeting system has often employed a unit inwhich a microphone and a speaker are integrally formed as one body (inFIG. 1, the microphone 101 a and the speaker 102 a are integrally formedas one body and the microphone 101 b and the speaker 102 b areintegrally formed as one body). In the following description, this unitwill be referred to as a “microphone/speaker integrated unit” forsimplicity.

FIG. 2A is a perspective view showing an example of an arrangement of amicrophone/speaker integrated unit according to the related art, andFIG. 2B is a perspective view showing a place where themicrophone/speaker integrated unit shown in FIG. 2A is set. As shown inFIG. 2A, in this microphone/speaker integrated unit, a speaker 121 isdisposed with its front axis being upwardly faced toward the verticaldirection, while a plurality of microphones 122 are disposed around thespeaker 121 with the fronts being faced toward the horizontal direction(although only one microphone is shown in FIG. 2A because of the angleat which the microphone/speaker integrated unit is seen, an LED(light-emitting diode) lamp 123 for displaying the on and off state ofthe microphone is provided at the upper side of each microphone andthree LED lamps 123 with respect to the three microphones 122 are shownin FIG. 2A). As shown in FIG. 2B, this microphone/speaker integratedunit 124 is set at the center of a table 125 at which participants aresitting in the meeting room.

FIG. 3A is a front view showing another example of an arrangement of amicrophone/speaker integrated unit according to the related art. FIG. 3Bis a perspective view showing a place where the microphone/speakerintegrated unit shown in FIG. 3A is set. As shown in FIG. 3A, thismicrophone/speaker integrated unit includes a speaker 126 whose frontaxis is faced toward the horizontal direction, a microphone 127 whosefront is faced toward the same direction as that of the speaker 126 anda video camera 128 whose image-pickup lens is faced toward the samedirection as that of the speaker 126, all of which are integrally formedas one body. As shown in FIG. 3B, this microphone/speaker integratedunit 129 is set at a corner of the table 125 in such a manner that itmay be faced toward the center of the table 125.

FIG. 4 is a perspective view showing a further example of an arrangementof a microphone/speaker integrated unit according to the related art anda place where such microphone/speaker integrated unit is set. Thismicrophone/speaker integrated unit may be used by each participant inthe meeting. As shown in FIG. 4, this microphone/speaker integrated unitincludes a speaker 130, a microphone 131 and an operation switch 132 forturning on and turning off the microphone 131. The microphone/speakerintegrated unit is set in front of the seat of each participant (acontrol unit 133 for use in the videoconferencing system is set at acorner of the table 125, each microphone/speaker integrated unit isconnected to the control unit 133 and a video camera 134 is set on thecontrol unit 133 such that it may be faced toward the center of thetable 125).

The above-mentioned known systems (1) to (3), however, encounter withthe following disadvantages.

Specifically, according to the above-mentioned system (1), while thelevel at which a voice of a participant sitting at the seat close to thenon-directional microphone (approximately within 1 meter) is inputted tothe non-directional microphone is large as an absolute amount and alsowhich is large as a relative ratio to the input level of otherbackground noise, the level at which a voice of a participant sitting atthe seat distant from the non-directional microphone (approximatelylonger than 1 meter) is inputted to the non-directional microphone isconsiderably low as an absolute amount and also which is considerablylow as a relative ratio to the input level of other background noise.Therefore, the voice of the participant at the seat distant from thenon-directional microphone is not efficiently collected by thenon-directional microphone. As a result, when the participant seatingdistant from the non-directional microphone speaks, the voice of thespeaking participant cannot be emanated clearly from the speaker inanother meeting room at the remote location. Then, there is a risk thatthe meeting cannot progress smoothly.

As an improved example of the known system (1), if an auxiliarymicrophone that can be turned on and off by operation buttons is setnear the seat of the participant distant from the non-directionalmicrophone and this microphone is turned on when the participant speaks,the above-mentioned disadvantage can be removed. However, the microphoneshould be turned on and off each time the participant speaks. Moreover,since the positions at which the microphones are to be set and thenumber of microphones that should be set have to be changed in responseto the positions at which the participants are seated and the number ofparticipants at the meeting. Accordingly, there arises a newdisadvantage that operations of the microphone and the work for settingthe microphones will become cumbersome for users.

Next, according to the known system (2), while a voice of eachparticipant is inputted to one or two directional microphones at most,noises (sounds from an air-conditioner, sounds from a radiation fan of aprojector, etc.) spread to the entire meeting room are inputted to alldirectional microphones and thereby synthesized, so that a sound signalsupplied to an echo canceller increases the level of noise relative tothe level of a voice of a participant than an actual level. As a result,a voice of the participant cannot be clearly emanated from the speakerin another meeting room at a remote location. There is then a risk thatthe meeting cannot progress smoothly.

In the above-mentioned system (3), when particular noises (e.g., soundsproduced when someone turns over the pages in front of the directionalmicrophone, sounds produced when a door is opened or shut in front ofthe directional microphone, etc.) of high level are inputted to only onedirectional microphone, this directional microphone is selected, so thatthe speaker in another meeting room at a remote location emanates mainlysuch noises. As a consequence, a voice of the participant cannot beclearly outputted from the speaker in another meeting room at a remotelocation. There is then a risk that the meeting cannot progresssmoothly.

Further, the microphone/speaker integrated units shown in FIGS. 2 to 4according to the related-art cannot avoid the following disadvantages.

In the microphone/speaker integrated unit shown in FIG. 2, since soundsare upwardly outputted from the speaker 121, the sounds reached the earsof the participants after they had been reflected on the ceiling or wallof the meeting room. As a result, the participants in one meeting roomcannot clearly hear a voice of the participant in another meeting roomat a remote location (when someone in one meeting room is speaking, avoice of someone cannot be distinctly outputted from the speaker 126 ofthe microphone/speaker integrated unit 129 in another meeting room at aremote location). There is a risk that the meeting cannot progresssmoothly.

In general, when the power switch of the microphone/speaker integratedunit having the arrangement shown in FIG. 2 is turned on, all themicrophones 122 are turned on so that noises (sounds from theair-conditioner, sounds from the radiation fan of the projector, etc.)spread to the entire meeting room are all inputted to the microphone andthereby synthesized. As a consequence, since the level of the noiserelative to the level of the voice of a participant increases than anactual one, from this point of view, the speaker 126 of themicrophone/speaker integrated unit 129 in another meeting room at aremote location becomes unable to distinctly output the voice of theparticipant.

Moreover, in the microphone/speaker integrated unit shown in FIG. 2, thesound outputted from the speaker 121 is leaked toward the microphone 122and inputted to the microphone 122. Therefore, since the echo cancellers(echo cancellers 103 a, 103 b in FIG. 1) are requested to have highcapabilities to suppress echo or howl, a burden imposed upon developmentof software executed by the DSP comprising the echo cancellerunavoidably increases and a cost of a hardware circuit used as an echocanceller also increases.

Next, in the microphone/speaker integrated unit shown in FIG. 3, whenmany participants are attending the meeting (when the table 125 islarge), the level at which a voice of a participant distant from themicrophone/speaker integrated unit 129 is inputted into the microphone127 decreases as an absolute amount and also decreases as a relativeratio to the input level of other background noises. Therefore, a voiceof the participant distant from the microphone/speaker integrated unit129 is not collected efficiently by the microphone 127. Accordingly,when the participant distant from the microphone/speaker integrated unit129 is speaking, since a voice of the participant cannot be outputtedclearly from the speaker 126 of another microphone/speaker integratedunit 129 at a remote location, there is a risk that the meeting cannotprogress smoothly.

In the microphone/speaker integrated unit shown in FIG. 3, since thesound outputted from the speaker 126 is leaked toward the microphone 127and inputted to the microphone 127, the echo canceller is requested tohave a high capability. As a result, it is unavoidable that a burdenimposed upon development of the echo canceller increases and that a costof a hardware circuit used as the echo canceller increases.

Further, when many participants are attending a meeting (when the table125 is large), the output level of the speaker 126 should be increasedin order to enable the participant distant from the microphone/speakerintegrated unit 129 to catch the sounds generated from the speaker 126clearly. However, when the output level of the speaker 126 increases,since the level at which the sound leaked from the speaker 126 towardthe microphone 127 and inputted into the microphone 127 also increases,the echo canceller is further requested to have a high capability.

When the microphone/speaker integrated unit 129 is not set at the cornerof the table as shown in FIG. 3B but is set at the center of the table125, since voices of participants seated in the rear and side directionsof the microphone/speaker integrated unit 129 are not efficientlycollected by the microphone 127, the speaker 126 of anothermicrophone/speaker integrated unit 129 at a remote location cannotclearly output the voices of the participants sitting in thosedirections.

Even when the microphone/speaker integrated unit 129 is set at thecenter of the table 125, the output level of the speaker 126 should beincreased in order to enable the participants seated in the rear andside directions of the microphone/speaker integrated unit 129 to catchthe sounds generated from the speaker 126 clearly. As a result, the echocanceller is further requested to have a high capability.

Next, in the microphone/speaker integrated unit shown in FIG. 4, sincethe microphones 131 and the speakers 130 exist near individualparticipants, the participants can distinctly catch the voices of theparticipants in another meeting room at a remote location.

However, many microphone/speaker integrated units should be provided inaccordance with the number of the participants and hence a cost of theaudio input unit increases inevitably.

Further, since the participant who is to speak has to turn on themicrophone 131 by operating the operation switch 132 before theparticipant begins to speak and also the participant has to turn off themicrophone 131 by operating the operation switch 132 after theparticipant has finished speaking, such operations for turning on or offthe switch 132 become cumbersome for users.

In addition, since the positions at which the microphone/speakerintegrated units are set and the necessary number of microphone/speakerintegrated units are changed in response to the positions at which theparticipants are seated and the number of participants, a work forsetting the microphones become troublesome for users.

Also in the microphone/speaker integrated unit shown in FIG. 4, sincethe sound outputted from the speaker 130 is leaked toward the microphone131 and inputted into the microphone 131, the echo canceller isrequested to have a high capability so that a burden imposed upondevelopment of the echo canceller increases and that a cost of the audioinput unit also increases.

SUMMARY OF THE INVENTION

In view of the aforesaid aspects, it is an object of the presentinvention to provide an audio input unit, an audio input method and anaudio input and output unit in which a voice of a participant canconstantly be outputted clearly from another speaker at a remotelocation in a remote location meeting system such as a videoconferencingsystem.

It is another object of the present invention to provide an audio inputunit, an audio input method and an audio input and output unit in whichoperations for turning on and off microphones and a work for settingmicrophone can be simplified and prevented from becoming cumbersome.

It is a further object of the present invention to provide an audioinput unit, an audio input method and an audio input and output unit inwhich a burden imposed upon developing a highly efficient echo cancellerand a cost can be decreased.

According to an aspect of the present invention, there is provided anaudio input unit including two directional microphones disposed indirections with directivity being opposite to each other, the twodirectional microphones forming a pair and a plurality of the pairsbeing located in directions with directivity being shifted from eachother, comprising: cancellation means for mutually canceling soundcomponents of the same phase from sounds inputted to the two directionalmicrophones of the pair, extraction means for extracting soundcomponents of a voice band from sounds inputted to the directionalmicrophones of the pair, calculation means for calculating a differencebetween levels of sound components of the voice band extracted by theextraction means with respect to the two directional microphones of thepair and deciding a directional microphone having the larger level inthe pair which has the largest level difference and selection means forselecting sounds, in which by the cancellation means the soundcomponents with the same phase are canceled from sound inputted to thedirectional microphone decided by the calculation means, as a voice tobe inputted.

In this audio input unit, the two directional microphones disposed indirections with directivity being opposite to each other (i.e., havinghigh sensitivity relative to sounds introduced from the directionsopposite to each other) constitute one pair. Then, a plurality of pairsare located in directions with directivity being shifted from each other(with sensitivity relative to sounds introduced from the directionsdifferent from each other).

The cancellation means cancels sound components of the same phase fromthe sounds inputted to the two directional microphones in the same pair.Thus, noises spread to the entire meeting room (sounds from anair-conditioner, sounds from a radiation fan of a projector, etc.) arecanceled from the sounds inputted to the two directional microphones.

Also, the extraction means extracts sound components of respective voicebands from the sounds inputted into the directional microphones of eachpair. Then, the calculation means calculates a difference between theinputted levels of the sound components of the voice band and selects adirectional microphone having the larger level from the pair having thelargest level difference. As a result, one microphone which iscollecting a voice of a currently speaking participant at highestefficiency is decided from the directional microphones of each pair.

Accordingly, there is selected the sound in which sound components ofthe same phase (noises spread to the entire meeting room) are canceledby the selection means from the sound inputted from the directionalmicrophone selected by the calculation means (microphone which collectsa voice of a currently speaking participant at highest efficiency) as aninput voice.

As described above, according to this audio input unit, the microphoneis not selected based upon the levels of the sounds inputted into theindividual microphones, but the microphone which collects the voice ofthe currently speaking participant at highest efficiency is selectedbased upon the difference between the inputted levels of the soundcomponents of the voice band with respect to the two directionalmicrophones of each pair, and the sound in which the noise spread to theentire meeting room is canceled from the sound inputted into theselected microphone is selected as the input voice.

Consequently, in the remote location meeting system such as thevideoconferencing system, the speaker in another meeting room at aremote location can constantly output a voice of a participant clearly.Since this inputted voice is selected automatically, operations forturning on and off the microphone can be simplified. Moreover, since itis only necessary to set the directional microphones of each pair ofthis audio input unit at the center of the table at which participantsare sitting, for example, a work for setting the microphones can beprevented from becoming cumbersome.

It is preferable that this input unit further comprises: for example, aplurality of image-pickup means whose fronts are directed approximatelyin the same directions as the directions in which the pair of thedirectional microphones have directivity and selection means forselecting an image picked up by image-pickup means whose front isdirected toward approximately the same direction as the direction inwhich the directional microphone determined by the calculation means hasdirectivity.

Thus, a picture (i.e., picture in which the participant is seen best)picked up by the image pickup means, which is faced toward approximatelythe same direction as the direction in which the microphone collectingthe voice of the currently speaking participant at highest efficiencyhas directivity, is selected automatically.

Accordingly, when only one camera is set in each meeting room, thecamera has to be faced toward the currently speaking participant in amanual fashion in the videoconferencing system. According to the aspectof the present invention, such troublesome camera work is not requiredand the meeting will progress more smoothly.

According to another aspect of the present invention, there is providedan audio input method comprising the steps of: locating two directionalmicrophones in directions with directivity being opposite to each other,the two directional microphones forming a pair and a plurality of thepairs being located in directions with directivity being shifted fromeach other, canceling sound components of the same phase from soundsinputted to the two directional microphones of the pair, extractingsound components of the voice band from sounds inputted to thedirectional microphones of the pair, calculating a difference betweensound components of the voice band extracted by the extracting step withrespect to the two directional microphones of the pair and deciding adirectional microphone having the larger level in the pair which has thelargest level difference and selecting sounds, in which by the cancelingstep the sound components with the same phase are canceled from soundinputted to the directional microphone decided by the calculating step,as input voice.

According to this audio input method, in exactly the same way as theaforementioned audio input unit according to the present invention, inthe remote location meeting system such as the videoconferencing system,the speaker in another meeting room at a remote location can constantlyoutput a voice of a participant clearly, and operations for turning onand off the microphone and a work for setting the microphones can beprevented from becoming cumbersome.

It is also preferable that this audio input method further comprises thesteps of: locating a plurality of image-pickup means whose fronts aredirected approximately in the same directions as the directions in whichthe pair of the directional microphone have directivity and selecting animage picked up by image-pickup means whose front is directed towardapproximately the same direction as the direction in which thedirectional microphone decided by the calculating step has directivity.

According to this audio input method, since the picture in which thecurrently speaking participant is seen best is selected automatically,the meeting will progress more smoothly.

According to a further aspect of the present invention, there isprovided an audio input and output unit (microphone/speaker integratedunit) comprising: a plurality of directional microphones disposed abovea speaker such that the microphones are faced toward directions withdirectivity being approximately perpendicular to a front axis of thespeaker, a reflective member provided between the speaker and theplurality of directional microphones to reflect sounds outputted fromthe speaker in the direction approximately perpendicular to a front axisof the speaker, and a shielding member provided between the speaker andthe plurality of directional microphones for separating the speaker andthe plurality of directional microphones from each other.

In this audio input and output unit, the reflective member forreflecting the sounds outputted from the speaker in the directionapproximately perpendicular to the front axis of the speaker existsbetween the speaker and a plurality of directional microphones.Accordingly, when this audio input and output unit is set at the tablein the meeting room such that the front axis of the speaker may be facedtoward the vertical direction, the sounds from the speaker are reflectedin the approximately horizontal direction by this reflective member.

Consequently, since the sounds from the speaker reach the participant'sears without reflecting on the ceiling or walls of the meeting room and,the speaker in another meeting room at a remote location can output theclear voice of the participant.

Moreover, in this audio input and output unit, a plurality ofdirectional microphones are provided in such a manner that themicrophones are faced toward directions with directivity beingapproximately perpendicular to the front axis of the speaker. Therefore,when this audio input and output unit is set on the table in the meetingroom such that the front axis of the speaker is faced toward thevertical direction, the directions in which these directionalmicrophones have directivity are approximately the horizontal direction(direction toward the participants at the table).

Consequently, since these directional microphones can collect voices ofrespective participants at high efficiency, the voice of the participantcan be clearly outputted from the speaker of another audio input andoutput unit at a remote location.

Moreover, since it is only necessary to set this audio input and outputunit at the center of the table at which participants are sitting, forexample, a cost can be decreased and a work for setting the microphonesand the operation can be prevented from becoming cumbersome.

Further, in this audio input and output unit, since the shielding memberfor separating the speaker and a plurality of directional microphonesexists between the speaker and these directional microphones, the amountof sounds leaked toward these directional microphones of soundsoutputted from the speaker can be decreased considerably. Therefore,since the level at which the sound from the speaker is inputted to thedirectional microphone is lowered considerably, echo and howl can besuppressed considerably without the processing of the echo canceller.

As a result, since the echo canceller itself is not required to havehigher capability, a burden imposed upon development of softwareexecuted by a DSP comprising the echo canceller can be alleviated and acost of a hardware circuit used as the echo canceller can be decreased.

Further, since the level at which the sound from the speaker is inputtedinto the directional microphone is lowered, a voice of a participant canbe collected by the directional microphone at high efficiency.

The reflective member may include, for example, a conical member withthe vertex of the circular cone thereof being faced toward the directionof the speaker, disposing a central axis of the circular coneapproximately aligned with the front axis of the speaker.

Further, in this audio input and output unit, it is preferable that, forexample, a plurality of directional microphones may comprise a pair ofdirectional microphones disposed in directions with directivity beingopposite to each other and a plurality of the pairs are located indirections with directivity being shifted from each other.

When the audio input and output unit in which a plurality of directionalmicrophones are disposed as described above is set at the center of thetable in the meeting room, voices of participants can be collected bythese directional microphones more efficiently.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an outline of a generalvideoconferencing system;

FIG. 2A is a perspective view showing an arrangement of amicrophone/speaker integrated unit according to the related art;

FIG. 2B is a pictorial perspective representation showing the manner inwhich the microphone/speaker integrated unit shown in FIG. 2A is to beset in a meeting room;

FIG. 3A is a front view showing an arrangement of a microphone/speakerintegrated unit according to the related art;

FIG. 3B is a pictorial perspective representation showing the manner inwhich the microphone/speaker integrated unit shown in FIG. 3A is to beset in a meeting room;

FIG. 4 is a perspective view showing an arrangement of amicrophone/speaker integrated unit according to the related art and themanner in which the microphone/speaker integrated units are to be set ina meeting room;

FIG. 5 is a front view showing, partly in a cross-sectional fashion, anoutward appearance of a microphone/speaker portion of an audio input andoutput unit to which the present invention can be applied;

FIG. 6 is a plan view showing an outward appearance of amicrophone/speaker portion of an audio input and output unit to whichthe present invention can be applied;

FIG. 7 is a perspective view schematically showing a microphone/speakerportion of an audio input and output unit to which the present inventioncan be applied;

FIG. 8 is a block diagram showing a circuit arrangement of a signalprocessing system of an audio input and output unit to which the presentinvention can be applied;

FIG. 9 is a flowchart for explaining processing executed-by acalculating circuit shown in FIG. 8;

FIG. 10 is a block diagram showing an outline of a videoconferencingsystem using an audio input and output unit to which the presentinvention can be applied;

FIG. 11 is a perspective view showing the position where the audio inputand output unit is to be set in the videoconferencing system shown inFIG. 10;

FIG. 12 is a schematic diagram showing a positional relationship betweena participant and microphones;

FIG. 13 is a front view showing, partly in a cross-sectional fashion, afirst modified example of an audio input and output unit to which thepresent invention can be applied;

FIG. 14 is a schematic block diagram showing a second modified exampleof an audio input and output unit to which the present invention can beapplied;

FIG. 15 is a flowchart for explaining the processing executed by a DSPshown in FIG. 14;

FIG. 16 is a front view showing, partly in a cross-sectional fashion, athird modified example of an audio input and output unit to which thepresent invention can be applied;

FIG. 17 is a plan view showing the third modified example of the audioinput and output unit to which the present invention can be applied;

FIG. 18 is a schematic block diagram showing the third modified exampleof the audio input and output unit to which the present invention can beapplied;

FIG. 19 is a block diagram showing the third modified example of theaudio input and output unit to which the present invention can beapplied;

FIG. 20 is a plan view showing a fourth modified example of an audioinput and output unit to which the present invention can be applied;

FIG. 21 is a plan view showing the fourth modified example of the audioinput and output unit to which the present invention can be applied;

FIG. 22 is a plan view showing a fifth modified example of an audioinput and output unit to which the present invention can be applied; and

FIG. 23 is a plan view showing the fifth modified example of the audioinput and output unit to which the present invention can be applied.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be described concretely with reference to thedrawings.

FIGS. 5 and 6 are a front view (partly in a cross-sectional fashion) anda plan view showing an outward appearance of a microphone/speakerportion of an audio input and output unit to which the present inventioncan be applied, respectively. FIG. 7 is a perspective view schematicallyshowing an outward appearance of this microphone/speaker portion.

This audio input and output unit is a unit that can be used in a remotelocation meeting system such as a videoconferencing system, in which amicrophone and a speaker are integrally formed (that is, a unit in whicha microphone for inputting a voice of a participant within a meetingroom and a speaker for outputting a voice of a participant in anothermeeting room are integrally formed as one body).

As illustrated, in this audio input and output unit, a dynamic speaker 6is accommodated within a cylindrical enclosure 5 having a diameter ofapproximately 150 mm in such a manner that the front axis of the dynamicspeaker 6 is upwardly faced toward the vertical direction.

On the upper edge portion of the enclosure 5, long supports 7 which areextending in the vertical direction are attached to two placessymmetrical to the front axis of the speaker 6, respectively. The longsupports 7 may be made of resin or metal having rigidity. On the upperside of the enclosure 5A, reflective plate 4 of a circular cone shapehaving a diameter of approximately 199 mm is attached to the upper endportions of the supports 7 by screws in such a manner that a vertex ofthe circular cone is faced toward the downward direction and that thecentral axis of the circular cone is approximately aligned with thefront axis of the speaker 6.

A distance from the vertex of the reflective plate 4 to the position atwhich the reflective plate 4 is attached to the upper end portions ofthe supports 7 by screws, with respect to the central axis direction, isslightly shorter than the height of the support 7. As a consequence, thevertex of the reflective plate 4 can be brought to the positionsufficiently close to a diaphragm of the speaker 6 within a range not incontact with the diaphragm of the speaker 6. The reflective plate 4 ismade of ABS (acrylonitrile-butadiene-styrene) resin.

As shown in FIG. 5, a disk-like shielding plate 3 having a diameter ofapproximately 300 mm is attached to the upper side of the reflectiveplate 4 across a cushion material 2 in such a manner that its platesurface is approximately located within a horizontal plane and that thecentral axis of the disk is approximately aligned with the central axisof the reflective plate 4. This disk-like shielding plate 3 is also madeof ABS resin.

The shielding plate 3 has a through hole at its central portion of theplate surface, and a columnar support 8 (made of resin or metal havingrigidity) extending in the vertical direction is attached to the upperside of the shielding plate 3 such that its lower end portion isextended through this hole. A disk-like member 9 (made of resin or metalhaving rigidity) having a diameter of approximately 30 mm is attached tothe upper end portion of the support 8 in such a manner that the centralaxis of the disk is approximately aligned with the central axis of thesupport 8.

A disk-like member 11 (made of resin or metal having rigidity) having adiameter of approximately 30 mm is attached to the upper side of themember 9 in such a manner that the central axis of the disk isapproximately aligned with the central axis of the support 8. A distancefrom the lower end portion of the support 8 to the upper end portion ofthe member 11 along the vertical direction is approximately 65 mm.

A pair of holes are bored through the peripheral edge portion of theplate surface of the member 11 at its four places which are distant atequal intervals from each other, and latches 12 a to 12 d having annularportions are attached to the member 11 through the above-mentioned fourholes.

As shown in FIG. 6, a unidirectional microphone (hereinafter simplyreferred to as a “microphone”) 1 a having a length of approximately 94mm and a diameter of approximately 10 mm and which has directivity inthe front direction is held within the approximately horizontal plane ofthe disk-like member 11 at its rear end portion latched by the latch 12a in such a manner that its front is nearly opposite to the central axisof the disk-like member 11 as seen from the latch 12 a.

A microphone 1 b of the same type as the microphone 1 a is held withinthe approximately horizontal plane of the disk-like member 11 at itsrear end portion latched by the latch 12 b located at the symmetricalposition to the latch 12 a with respect to the central axis of thedisk-like member 11 in such a manner that its front is nearly oppositeto the central axis of the disk-like member 11 as seen from the latch 12b (i.e., the directivity is set to the opposite direction of themicrophone 1 a).

A microphone 1 c of the same type is held within the approximatelyhorizontal plane of the disk-like member 11 at its rear end portionlatched by the latch 12 c in such a manner that its front is nearlyopposite to the central axis of the disk-like member 11 as seen from thelatch 12 c (i.e., the directivity is shifted by 90° from that of themicrophone 1 a or 1 b).

A microphone 1 d of the same type is held within the approximatelyhorizontal plane of the disk-like member 11 at its rear end portionlatched by the latch 12 d located at the symmetrical position to thelatch 12 c with respect to the central axis of the disk-like member 11in such a manner that its front is nearly opposite to the central axisof the disk-like member 11 as seen from the latch 12 d (i.e., thedirectivity is shifted by 90° from that of the microphone 1 a or 1 b andalso is set to the opposite direction of the microphone 1 c).

As described above, and as shown in FIG. 7, in this audio input andoutput unit, a pair of microphones (referred to as a “pair A”)comprising the two unidirectional microphones 1 a and 1 b located indirections with directivity being opposite to each other and a pair ofmicrophones (referred to as a “pair B”) comprising the twounidirectional microphone 1 c and 1 d located in directions withdirectivity being opposite to each other are disposed above the upperside of the speaker 6 whose front axis is faced toward the verticaldirection through the reflective plate 4 and the shielding plate 3 insuch a manner that directivity of the microphones are shifted byapproximately 90° from each other.

FIG. 8 is a block diagram showing a circuit arrangement of a signalprocessing system of an audio input and output unit to which the presentinvention can be applied. This signal processing system is accommodatedwithin a case (not shown) which is externally attached to themicrophone/speaker portion shown in FIGS. 2 to 4. Alternatively, asanother example, this signal processing system may be accommodatedwithin a space produced in the inside of the enclosure 5 of themicrophone/speaker portion shown in FIGS. 5 to 7.

Referring to FIG. 8, sound signals outputted from the microphones 1 a, 1b comprising the pair A are supplied to this signal processing system,in which the sound signals are respectively amplified by microphoneamplifiers 21 a, 21 b and supplied to positive (plus) input terminals ofsubtractors 22 a, 22 b and also supplied to an in-phase sound detectingcircuit 23.

The in-phase sound detecting circuit 23 is a circuit for extractingsound components of the same phase from two sound signals by comparingthe levels of the inputted two sound signals, the frequency componentsof the inputted two sound signals and the phases of the inputted twosound signals, and the circuit may be comprised of a digital filter oran analog filter. Sound component signals extracted by the in-phasesound detecting circuit 23 are supplied to negative (minus) inputterminals of the subtractors 22 a, 22 b.

Sound signals inputted to the microphones 1 c, 1 d comprising the pair Bare respectively amplified by microphone amplifiers 21 c, 21 d,whereafter they are respectively supplied to positive input terminals ofsubstractors 22 c, 22 d and an in-phase sound detecting circuit 24.

The in-phase detecting circuit 24 is a circuit having the same circuitarrangement as that of the in-phase sound detecting circuit 23. Soundcomponent signals extracted by the in-phase sound detecting circuit 24are supplied to negative input terminals of the subtractors 22 c, 22 d,respectively.

Sound signals outputted from the subtractors 22 a to 22 d are suppliedto switch elements 27 a to 27 d, respectively. Output terminals of theswitch elements 27 a to 27 d are connected to an audio output terminal28 of this audio input and output unit. A signal is supplied to controlinput terminals of the switch elements 27 a to 27 d from a calculatingcircuit 26 which will be described later on.

On the other hand, the sound signals outputted from the microphones 1 a,1 b comprising the pair A are also supplied through the microphoneamplifiers 21 a, 21 b to voice band filters 25 a, 25 b, respectively.The sound signals outputted from the microphones 1 c, 1 d comprising thepair B are supplied through the microphone amplifiers 21 c, 21 d tovoice band filters 25 c, 25 d, respectively.

The voice band filters 25 a to 25 d are band-pass filters having apassage of frequency bands of man's voice (100 Hz to 4 kHz). Soundsignals that have passed through the voice band filters 25 a to 25 d aresupplied to the calculating circuit 26.

The calculating circuit 26 is a circuit for executing steps shown inFIG. 9 repeatedly. In this processing, first, as shown in FIG. 9, at afirst step S1, the calculating circuit 26 calculates a differencebetween the levels of the sound signals from the voice band filters 25 aand 25 b (i.e., difference between the levels of the voice band signalsfrom the microphones 1 a and 1 b comprising the pair A) and alsocalculates a difference between the levels of the sound signals from thevoice band filters 25 c and 25 d (i.e., difference between the levels ofthe voice band signals from the microphones 1 c and 1 d comprising thepair B).

At the next step S2, the calculating circuit 26 decides the pair inwhich an absolute value of this signal level difference is large bycomparing the pairs A and B. Then, control goes to the next step S3,whereat the calculating circuit 26 decides one microphone having thelarger signal level by comparing two microphones comprising the pairthus determined.

At the next step S4, of the switch elements 27 a to 27 d, thecalculating circuit 26 supplies a signal to turn on only a switchelement corresponding to the microphone thus decided (if the decidedmicrophone is the microphone 1 a, for example, then the signal issupplied to only the switch element 27 a).

Then, at the next step S5, of the LED (light-emitting diode) units 29 ato 29 d, shown in FIG. 8, respectively provided on the surface of thecase of this audio input and output unit in response to the microphones1 a to 1 d, the calculating circuit 26 supplies a signal for turning onthe LED to only the LED display unit corresponding to the microphonethus decided.

This calculating circuit 26 may be constituted by combining a pluralityof hardware circuits (subtractor, comparator or the like) havingfunctions corresponding to the individual processing steps S1 to S5,respectively or may be constituted by installing software, which is usedto execute the steps S1 to S5, on the DSP.

As shown in FIG. 8, an audio signal inputted to an audio input terminal30 of this audio input and output unit is supplied to the speaker 6through a speaker amplifier 31.

FIG. 10 is a block diagram showing an outline of a videoconferencingsystem using this audio input and output unit wherein elements and partsidentical to those of FIG. 1 are denoted by identical referencenumerals.

As shown in FIG. 10, the meeting room Ra is provided with this audioinput and output unit 41 and also includes the echo canceller 103 a, thevideo camera 104 a, the projector 105 a, the codec 106 a and the DSU 107a.

The meeting room Rb, which is located at the spot. remote from themeeting room Ra, is also provided with this audio input and output unit41 and also includes the echo canceller 103 b, the video camera 104 b,the projector 105 b, the codec 106 b and the DSU 107 b. The DSU 107 aand the DSU 107 b are connected to each other by the dedicated line 108or the ISDN 109.

As shown in FIG. 11, in each of the meeting rooms Ra and Rb, themicrophone/speaker portion of the audio input and output unit 41 is setat the center of a table 110 where all participants are to be seated.

The audio signal outputted from the audio output terminal 28 of theaudio input and output unit 41 located within the meeting room Ra isinputted to the audio input terminal 30 of the audio input and outputunit 41 in the meeting room Rb through the echo canceller 103 a, thecodec 106 a, the DSU 107 a, the dedicated line 108 or the ISDN 109, theDSU 107 b, the codec 106 b and the echo canceller 103 b, sequentially.The audio signal outputted from the audio output terminal 28 of theaudio input and output unit 41 within the meeting room Rb is alsoinputted to the audio input terminal 30 of the audio input and outputunit 41 in the meeting room Ra in the same manner.

Next, the manner in which the meeting is progressing in thevideoconferencing system shown in FIG. 10 will be described.

As shown in FIG. 12, for example, let it be assumed that, ofparticipants seated at the table 110 (FIG. 11) within the meeting roomRa, a participant P, who is sitting at the seat closest to the front ofthe microphone 1 a of the microphones 1 a to 1 d of the audio input andoutput unit 41, is speaking.

At this time, the voice of this participant P and other background noiseare inputted to the respective microphones 1 a to 1 d of the audio inputand output unit 41. Then, the subtractors 22 a, 22 b and the in-phasesound detecting circuit 23 subtract signals of sound components of thesame phase from the outputted audio signals from the microphones 1 a, 1b comprising the pair A, whereby a signal of sound components equallyinputted to the microphones 1 a, 1 b (such as sounds of anair-conditioner and radiation fans of the projector 105 a which arenoises spread to the entire meeting room Ra.) are canceled from theoutputted sound signals from the two microphones 1 a, 1 b which arelocated in directions with directivity being opposite to each other.

Similarly, the subtractors 22 c, 22 d and the in-Zphase sound detectingcircuit 24 subtract signals of sound components of the same phase fromthe outputted sound signals from the microphones 1 c, 1 d comprising thepair B, whereby signals of sounds such as sounds of the air-conditionerand the radiation fans of the projector 105 a which are noises spread tothe entire meeting room Ra are canceled from the outputted sound signalsof the two microphones 1 c, 1 d located in directions with directivitybeing opposite to each other.

At that time, since the seat of the participant P is closest to thefront of the microphone 1 a (that is, the seat most distant from thefront of the microphone 1 b), a voice of the participant P is collectedby the microphone 1 a of the microphones 1 a to 1 d at highestefficiency and is hardly collected by the microphone 1 b.

Accordingly, when the calculating circuit 26 executes the calculationprocessing shown in FIG. 9 based upon the outputted sound signals fromthe voice band filters 25 a to 25 d, since the calculating circuit 26decides the pair A as the pair which has the larger absolute value ofthe difference between the levels of the voice band signals at the stepsS1, S2 and the calculating circuit 26 decides the microphone 1 a as themicrophone having the higher level of the voice band signal at the stepS3, the calculating circuit 26 supplies the signal for turning on onlythe switch element 27 a of the switch elements 27 a to 27 d at the stepS4.

As a result, in the audio input and output unit 41 within the meetingroom Ra, the sound that is inputted to the microphone 1 a which collectsa voice of the participant P at highest efficiency of the microphones 1a to 1 d, and that is then subtracted noises spread to the entiremeeting room Ra by the subtractor 22 a and the in-phase sound detectingcircuit 23 is selected to be an inputted voice at the switch elements 27a to 27 d, and the signal of the sound thus selected is outputted fromthe audio output terminal 28.

The speaker 6 of the audio input and output unit 41 within anothermeeting room Rb can output the sound in which the noise spread to theentire meeting room Ra is canceled from the sound inputted to themicrophone 1 a of the audio input and output unit 41 within the meetingroom Ra.

Thus, the speaker 6 of the audio input and output unit 41 within themeeting room Rb can output a clear voice of the participant P.

Although we have so far described the example in which the participantseated closest to the front of the microphone 1 a of the microphones 1 ato 1 d speaks, the present invention is not limited to theabove-mentioned example and the following variant is also possible. Whena participant seated closest to the front of the microphone 1 b, 1 c or1 d speaks or when the participant P continues speaking while moving toa seat closest to the front of the microphone 1 b, 1 c or 1 d, the audioinput and output unit 41 within the meeting room Ra may select a soundsignal in which the noise spread to the entire meeting room Ra iscanceled from the sound inputted to the microphone 1 b, 1 c or 1 d andmay output the selected sound signal from the audio output terminal 28in the same way.

Therefore, the speaker 6 of the audio input and output unit 41 withinthe meeting room Rb can constantly output a clear voice of a participantin the meeting room Ra.

While we have so far described the example in which a participant withinthe meeting room Ra spoke, the present invention is not limited to theabove-mentioned example. That is, when a participant in the meeting roomRb speaks, the speaker 6 of the audio input and output unit 41 withinthe meeting room Ra can constantly output a clear voice of theparticipant who is speaking in the meeting room Rb.

As described above, according to this audio input unit, since themicrophone which can collect a voice of a speaker at highest efficiencyis decided based upon the difference between the inputted levels of thevoice band sound components with respect to two directional microphonescomprising each pair A, B and the sound in which the noise spread to theentire meeting room is canceled from the sound inputted to the decidedmicrophone is selected as the inputted sound, the speaker in anothermeeting room at a remote location can constantly output a clear voice ofa participant.

Further, according to this audio input unit, as shown in FIGS. 5 to 7,since the reflective plate 4 having the circular cone shape exists abovethe speaker 6, the sound upwardly outputted from the speaker 6 arereflected in the horizontal direction by the reflective plate 4. As aconsequence, the sound from the speaker 6 can reach the ears ofparticipants without being reflected on the ceiling or walls of themeeting room. From this standpoint, participants are able to catch aclear voice of a participant in another meeting room at the remotelocation from the speaker 6 as well.

Moreover, according to this audio input unit, as shown in FIGS. 5 to 7,since the shielding plate 3 exists above the reflective plate 4 so as toseparate the microphones 1 a to 1 d and the reflective plate 4, of thesounds reflected on the reflective plate 4, the amount of sounds leakedto the microphones 1 a to 1 d can be decreased considerably, so that thelevels of the sound inputted to the microphones 1 a to 1 d afteroutputted from the speaker 6 can be lowered considerably.

In addition, since the microphones 1 a to 1 d are brought to the samepositional relationship relative to the speaker 6, the sounds inputtedto the microphones 1 a to 1 d from the speaker 6 become the soundshaving the same phase. Accordingly, the sounds inputted to themicrophones 1 a to 1 d at very low level after outputted from thespeaker 6 also can be canceled by the subtractors 22 a to 22 d and thein-phase sound detecting circuits 23, 24 shown in FIG. 8.

Furthermore, since the audio input and output unit 41 is set at thecenter of the table 110 as shown in FIG. 11 (i.e., the speaker 6 islocated close to each participant), the participant in one meeting roomcan clearly catch the voice of a participant in another meeting room atthe remote location without increasing the level of the sound outputtedfrom the speaker 6. Therefore, from this standpoint, the level of thesound inputted to the microphones 1 a to 1 d after outputted from thespeaker 6 can be further decreased.

Accordingly, echo that is a phenomenon in which the sound inputted tothe microphones 1 a to 1 d of the audio input and output unit 41 in onemeeting room is again outputted from the speaker 6 of the audio inputand output unit 41 in the same meeting room through the audio input andoutput unit 41 in another meeting room, and howl caused by the echo canbe suppressed considerably without being processed by the echocancellers 103 a, 103 b.

As a consequence, since the echo cancellers 103 a, 103 b are notrequired to have high capability, a burden imposed when softwareexecuted by the DSP comprising the echo cancellers 103 a, 103 b isdeveloped can be alleviated and the costs of the hardware circuits foruse as the echo cancellers 103 a, 103 b can be decreased as well.

Since the level at which the sound from the speaker 6 is inputted to themicrophones 1 a to 1 d is very low and the audio input and output unit41 is set at the center of the table 110 at which the participants areseated as shown in FIG. 11 (the microphones 1 a to 1 d are placed closeto each of the participants and the directions in which the microphones1 a to 1 d have directivity are faced toward the directions of theparticipants), the level at which a voice of each participant isinputted to the microphones 1 a to 1 d may increase as an absoluteamount and may also increase relative to the input level of thebackground noise (sounds from the speaker 6, sounds from theair-conditioner, sounds from the exhaust fan of the projector, etc.).Thus, the microphones 1 a to 1 d can efficiently collect a voice of theparticipant.

Next, several modified examples of the audio input and output unit willbe described.

FIG. 13 is a front view (partly in a cross-sectional fashion) showing afirst modified example in which the shape of the reflective plateprovided above the speaker 6 is changed. In FIG. 13, elements and partsidentical to those of FIG. 5 are denoted by identical referencenumerals.

In the first modified example, as shown in FIG. 13, instead of theconical reflective plate 4 shown in FIG. 5, a reflective plate 51, inwhich an edge portion curved in the same direction as the vertex of thecircular cone is formed around the conical portion, is attached to theupper end portions of the respective supports 7 by screws in such amanner that the vertex of the circular cone is faced toward the lowerdirection and that the central axis of the circular cone is nearlyaligned with the front axis of the speaker 6. A curvature radius at theedge portion of the reflective plate 51 is approximately 22.5 mm and thelength of this edge portion extending along the vertical direction isapproximately 22.5 mm as well.

The rest of the portion other than the reflective plate 51 in FIG. 13has the same structure as that shown in FIG. 5.

According to the first modified example, since the edge portion of thereflective plate 51 covers the speaker 6 like a shade, of soundsreflected on the reflective plate 51, the amount of sounds leaked to themicrophones 1 a to 1 d can further be decreased so that the level of thesounds inputted to the microphones 1 a to 1 d after outputted from thespeaker 6 can further be lowered.

FIG. 14 is a schematic block diagram showing a second modified examplein which one DSP may realize all functions of the subtractors 22 a to 22d, the in-phase sound detecting circuits 23, 24, the voice band filters25 a to 25 d and the switch elements 27 a to 27 d of the circuit shownin FIG. 8. In FIG. 14, elements and parts identical to those of FIG. 8are denoted by identical reference numerals.

In the second modified example, the sound signals outputted from themicrophones 1 a, 1 b comprising the pair A are respectively amplified bythe microphone amplifiers 21 a, 21 b and converted into digital signalsby A/D (analog-to-digital) converters 61 a, 61 b, whereafter they aresupplied to a DSP 62. The sound signals outputted from the microphones 1c, 1 d comprising the pair B are respectively supplied through themicrophone amplifiers 21 c, 21 d and A/D converters 61 c, 61 d to theDSP 62 as well.

Software for causing the DSP 62 to repeatedly execute processing stepsshown in FIG. 15 is installed on the DSP 62. In this processing, first,as the processing corresponding to the functions of the subtractors 22 ato 22 d and the in-phase sound detecting circuits 23, 24, soundcomponents having the same phase are extracted from the two soundsignals supplied from the A/D converters 61 a, 61 b, and soundcomponents having the same phase are subtracted from the two soundsignals. Similarly, sound components having the same phase are extractedfrom the two sound signals supplied from the A/D converters 61 c, 61 dand sound components having the same phase are subtracted from the twosound signals at a step S11.

At the next step S12, as the processing corresponding to the functionsof the voice band filters 25 a to 25 d shown in FIG. 8, sound componentsof the frequency band of man's voice (100 Hz to 4 kHz) are respectivelyextracted from the sound signals supplied from the A/D converters 61 ato 61 d.

Subsequently, control goes to steps S13 to S15, whereat the sameprocessing as that of the steps S1 to S3 shown in FIG. 9 is executed asthe processing equivalent to the function of the calculating circuit 26shown in FIG. 8.

At a step S16, as the processing equivalent to the functions of thecalculating circuit 26 and the switch elements 27 a to 27 d shown inFIG. 8, the sound signal whose in-phase sound components had beensubtracted at the step S11 from the sound signal transmitted from theA/D converter corresponding to the microphone decided at the step S15(e.g., when the microphone 1 a is decided, that is the A/D converter61a) is supplied to a D/A converter 63 shown in FIG. 14.

Then, control goes to the next step S17, whereat the DSP 62 executes thesame processing as that of the step S5 shown in FIG. 9 equivalent to thefunction of the calculating circuit 26 shown in FIG. 8.

As shown in FIG. 14, the sound signal that has been supplied to the D/Aconverter 63 at the processing step S16 of the DSP 62 is converted intoan analog signal by the D/A converter 63 and outputted from the audiooutput terminal 28.

According to the second modified example, since the circuit can be madesmall in size, the whole audio input and output unit can be reduced insize.

FIGS. 16, 17, 18 and 19 are respectively a front view (partly in across-sectional fashion), a plan view, a circuit block diagram and asystem block diagram showing a third modified example in which not onlythe microphones and the speakers but also video cameras are integrallyformed as one body of the audio input and output unit. In FIGS. 16, 17,18 and 19, elements and parts identical to those of FIGS. 5, 6, 8, 10are denoted by identical reference numerals.

In the third modified example, as shown in FIGS. 16 and 17, instead ofthe member 11 shown in FIG. 5, a disk-like member 71 having the samestructure as that of the member 11 and having a through-hole extendedthrough the central portion of the plate surface is attached to theupper side of the member 9 through the cushion material 10.

A columnar support 72 (made of either resin or metal with rigidity)extended in the vertical direction is attached to the upper side of themember 9 through the through-hole extended through the central portionof the member 71. The upper end portion of the support 71 in thevertical direction has a height higher than those of the microphones 1 ato 1 d.

A member 73 (made of either resin or metal with rigidity) havingapproximately a square-like shape is attached to the upper end portionof this support 72. Four CCD (charge-coupled device) cameras 74 a to 74d are respectively attached onto this member 73 such that their frontsare faced toward the same directions as those of the microphone 1 a to 1d.

The structure of portions other than the member 71, the support 72, themember 73 and the CCD cameras 74 a to 74 d shown in FIGS. 16 and 17 arethe same as those shown in FIGS. 5 and 6.

In the third modified example, as shown in FIG. 18, image signalsoutputted from the CCD cameras 74 a to 74 d are respectively supplied toswitch elements 75 a to 75 d. Output terminals of the switch elements 75a to 75 d are connected to an image output terminal 76 of this audioinput and output unit.

The signal supplied from the calculating circuit 26 to the LED displayunits 29 a to 29 d to turn on the LED lamps at the step S5 shown in FIG.9 is also supplied to control input terminals of the switch elements 75a to 75 d as signals for turning on the respective switches.

In the third modified example, as shown in FIG. 19, the meeting room Raincludes an audio input and output unit 81 according to the thirdmodified example and further includes the echo canceller 103 a, theprojector 105 a, the codec 106 a and the DSU 107 a. Another meeting roomRb located at the spot remote from the meeting room Ra also includes theaudio input and output unit 81 according to the third modified exampleand further includes the echo canceller 103 b, the projector 105 b, thecodec 106 b and the DSU 107 b.

An image signal outputted from the image output terminal 76 of the audioinput and output unit 81 within the meeting room Ra is sequentiallysupplied through the codec 106 a, the DSU 107 a, the dedicated line 108or the ISDN 109, the DSU 107 b and the codec 106 b to the projector 105b in another meeting room Rb. An image signal outputted from the imageoutput terminal 76 of the audio input and output unit 81 within anothermeeting room Rb is similarly supplied to the projector 105 a in themeeting room Ra.

According to the third modified example, when the participant P seatedclosest to the front of the microphone 1 a of the microphones 1 a to 1 dspeaks as shown in FIG. 12, for example, only the switch element 75 a inthe switch elements 75 a to 75 d is turned on, whereby the image signalfrom the CCD camera 74 a which is faced to the same direction as themicrophone 1 a (i.e., the image of participant P is best picked up) isautomatically selected from the image signals from the CCD cameras 74 ato 74 d, then outputted from the audio input and output unit 81 andtransmitted to the projector in another meeting room.

As described above, according to the third modified example, the CCDcamera in which the speaking participant is best picked up isautomatically selected and the picture from the selected CCD camera isprojected by the projector in another meeting room.

Therefore, according to the known remote location meeting system inwhich only one camera is provided in each meeting room, the camera needsto be directed to a currently speaking participant to pick up the imageeach, time in a manual fashion. According to the third modified example,since such cumbersome operations for manipulating the camera is notrequired, the meeting will progress more smoothly.

FIGS. 20 and 21 are a front view (partly in a cross-sectional fashion)and a plan view respectively showing a forth example in which the numberand the layout of microphones are changed. In FIGS. 20 and 21, elementsand parts identical to those of FIGS. 5 and 6 are denoted by identicalreference numerals. FIGS. 22 and 23 are a front view (partly in across-sectional fashion) and a plan view respectively showing a fifthexample in which the number and the layout of microphones are changed.In FIGS. 22 and 23, elements and parts identical to those of FIGS. 5, 6,20 and 21 are denoted by identical reference numerals.

In the fourth modified example, instead of the member 11 shown in FIG.5, a disk-like member 91 (made of either resin or metal with rigidity)wider than the member 11 is attached to the upper side of the member 9through the cushion material 10 (although the portion below the cushionmaterial 10 is not shown in FIGS. 20 and 21, this portion has the samestructure as that shown in FIGS. 5 and 6).

A columnar support 92 (made of either resin or metal with rigidity)extending in the vertical direction is attached to the central portionof the plate surface of the member 91. The pair of microphones(aforementioned pair A) comprising the microphones 1 a and 1 b withdirectivity being opposite to each other, the pair of microphones(aforementioned pair B) comprising two microphones 1 c and 1 d withdirectivity similarly being opposite to each other and the pair ofmicrophones (now referred to as a “pair C”) comprising twounidirectional microphones 1 e and 1 f of the same type as themicrophones 1 a to 1 d and with directivity being opposite to each otherare mounted around the support 92 in such a manner that theirdirectivity are shifted by approximately 60° from each other.

Also in the fifth modified example, instead of the member 11 shown inFIG. 5, the member 91 is attached to the upper side of the member 9through the cushion material 10 (although the portion below the cushionmaterial 10 is not shown in FIGS. 22 and 23, this portion has the samestructure as that shown in FIGS. 5 and 6).

Six columnar supports 93 (made of either resin or metal with rigidity)extending in the vertical direction are attached at equal intervals tothe peripheral edge portion of the plate surface of the member 91. Thepair of microphones (aforementioned pair A) comprising the microphones 1a and 1 b with directivity being opposite to each other, the pair ofmicrophones (aforementioned pair B) comprising the two microphones 1 cand 1 d with directivity being opposite to each other and the pair ofmicrophones (aforementioned pair C) comprising the two microphones 1 eand 1 f with directivity being opposite to each other are attached tothese supports 93 in such a manner that their directivity are shifted byapproximately 60° from each other. A disk-like member 94 is attached tothe upper side of the pairs A, B, and C at the positions encircled bythe respective supports 93 as a lid.

Although not shown, the signal processing systems of the audio input andoutput units according to the fourth and fifth modified examples may beconstituted in such a manner that the signal processing system shown inFIG. 8, for example, may be changed in response to the three pairs,i.e., the pairs A, B, and C (a microphone amplifier, a subtractor, anin-phase sound detecting circuit, an voice band filter, a switch elementand the like for the pair C may be additionally provided and theprocessing described in FIG. 9 may be executed by the calculatingcircuit 26 with respect to the three pairs A, B, and C, respectively).

According to the fourth and fifth modified examples, since the number ofthe microphone pairs increases, even when many participants attend themeeting, it becomes possible to collect voices of the participants moreefficiently.

While the present invention has been applied to the audio input andoutput unit including the signal processing system shown in FIG. 8 inthe above-mentioned embodiments, the present invention is not limited tothose embodiments and may be applied to an audio input and output unitwithout such signal processing system (that is, audio input and outputunit comprising only the microphone/speaker portion shown in FIGS. 5 to7).

When the audio input and output unit does not include this signalprocessing system, the microphones in the microphone/speaker portion maybe arranged in such a manner that the microphones may not comprise thepair such as the aforementioned pairs A or B (two microphones are notdisposed in directions with directivity being made opposite to eachother).

While the microphone/speaker portion is provided with the reflectiveplate of the circular cone shape in the above-mentioned embodiments, theshape of the reflective plate may be changed freely as long as thereflective plate can reflect sounds from the speaker toward thedirection approximately perpendicular to the front axis of the speaker.

While the microphone/speaker portion is provided with the disk-likeshielding plate in the above-mentioned embodiments, the shape of theshielding plate may be changed freely as long as the shielding plate canseparate the speaker and the microphones from each other (as long as theshielding plate can prevent sounds of the speaker from being leaked tothe microphones).

While the reflective plate and the shielding plate are provided in themicrophone/speaker portion as the separate members in theabove-mentioned embodiments, it is possible to provide one member havingboth functions of the reflective plate and the shielding plate in themicrophone/speaker portion.

While the present invention is used in the videoconferencing system inthe above-mentioned embodiments, the present invention can be employedin other remote location conference system than the videoconferencingsystem.

As described above, according to the audio input unit and the audioinput method of the present invention, in the remote location meetingsystem like the videoconferencing system, another speaker at the remotelocation can constantly output clear voices of participants and theoperations for manipulating the microphones and the work for setting theaudio input unit can be prevented from becoming cumbersome for users.

Further, according to the audio input unit and the audio input method ofthe present invention, since the picture in which the currently speakingparticipant is best picked up is automatically selected as the inputtedpicture, the meeting will progress more smoothly.

Furthermore, according to the audio input and output unit of the presentinvention, in the remote location meeting system like thevideoconferencing system, another speaker at the remote location canconstantly output clear voices of participants, a cost of the audioinput and output unit can be prevented from being increased, theoperations for manipulating the microphones, the work for setting theaudio input unit can be prevented from becoming cumbersome and a burdenand a cost of development of the echo canceller can be decreased.

Having described preferred embodiments of the invention with referenceto the accompanying drawings, it is to be understood that the inventionis not limited to those precise embodiments and that various changes andmodifications could be effected therein by one skilled in the artwithout departing from the spirit or scope of the invention as definedin the appended claims.

1. (canceled)
 2. (canceled)
 3. (canceled)
 4. (canceled)
 5. an audioinput and output unit comprising: a plurality of directional microphonesdisposed above a speaker such that the microphones are faced towarddirections with directivity being approximately perpendicular to a frontaxis of said speaker; a reflective member provided between said speakerand said purality of directional microphones to reflect sounds outputtedfrom said speaker in the direction approximately perpendicular to saidfront axis of said speaker; and a shielding member provided between saidspeaker and said plurality of directional microphones to separate saidspeaker and said plurality of directional microphones from each other.6. The audio input and output unit according to claim 5, wherein: saidreflective member includes a conical member and said conical member isdisposed in such a manner that the vertex of the circular cone thereofis faced toward the direction of said speaker and that a central axis ofsaid circular cone is approximately aligned with the front axis of saidspeaker.
 7. The audio input and output unit according to claim 6,wherein: said plurality of directional microphones comprise a pair ofdirectional microphones disposed in directions with directivity beingopposite to each other and said plurality of pairs are located indirections with directivity being shifted from each other.
 8. The audioinput and output unit according to claim 6, wherein: said plurality ofdirectional microphones comprise a pair of directional microphonesdisposed in directions with directivity being opposite to each other andsaid plurality of pairs are located in directions with directivity beingshifted from each other.